1. Field of the Invention
The present invention relates generally to methods for marking defects in thin film hard disks, and more particularly to the use of precise coordinates and DC erase on the hard disk to locate and identify the defect and utilizing ferromagnetic fluid for visual identification of the defect.
2. Description of the Prior Art
The detection, location and analysis of defects on the surface of hard disks has become an increasingly difficult problem where data bit sizes have decreased such that sub-micron sized asperities are of sufficient size to constitute defects. A read/write head may be used for the detection and location of such defects, as is taught in U.S. Pat. No. 4,635,139, entitled Asperity Burst Writer, issued Jan. 6, 1987 to Nguyen et al. Such asperity location and marking methods have provided adequate results in the past, however, the difficulty in locating and marking sub-micron sized defects has necessitated improved methods for disk marking for defect location. The present invention avoids writing, or erasing over a defect and avoids the application of ferromagnetic fluid on top of the defect where steps are taken to visually locate the defect.